General examples of a conventional retroreflective product 10 mainly include retroreflective products formed by applying heat and pressure to a transparent thermoplastic polymer sheet thus forming a cube-corner shape, or those made of two kinds of materials so that a cube-corner shape is formed using a thermosetting resin on one surface of a flexible polymer sheet.
Such a retroreflective product 10 has optical properties (the retroreflective function) in which incident light 11 enters a sheet of the retroreflective product 10, passes through a transparent polymer layer, and then is completely reflected off the inner surface of a cube-corner type retroreflective device such that reflected light 12 is emitted out backwards in a direction parallel to the incident light 11.
Thus, the retroreflective product 10 is variously processed for application to traffic signboards, safety clothes or safety indicators for construction work structures. However, the transparent thermoplastic polymer sheet chiefly used therein is disadvantageous because it easily tears due to its low tensile strength when used for purposes (e.g., signboards, banner advertisements, packages) requiring high tensile strength (10 kg/cm2 or more), such as a flex used for advertisements, and thus it is unsuitable for such purposes.
So, the retroreflective product is mainly used by attaching it to a target using an adhesive or through sewing.
In the case of a flex (a sheet in which a woven fabric is integratedly disposed in the middle portion of a white thermoplastic sheet) used for most signboards and billboards, it enables the signboard or billboard to be visible, at night time only when under external illumination or if an illuminator is attached to the back surface thereof. However, such a flex suffers because the information contained thereon is not sufficiently conveyed to people in the absence of electric power or an additional illuminator.